In the livestock industry and most importantly in the raising of hogs, it is important to determine the amount of backfat on an animal. Previously, this measurement was obtained by piercing the skin of the animal with a mechanical measuring tool. This mechanical method was undesirable due to the irritation and possible infection which the animal might suffer, and in some areas, this method has been made illegal. As an alternative, ultrasonic waves can be transmitted into the animal, and by measuring reflected echoes, the depth of various fat layers can be determined. Because such animals have various layers of tissue and fat, a single ultrasonic pulse transmitted into the animal produces multiple return echoes originating at the interface between such layers. The problem, therefore, unsolved by prior art devices, was to isolate the desired reflective pulses or echoes from unwanted echoes and produce an output display in a directly readable form which would immediately supply the measurement data without operator interpretation. Prior art devices have used oscilloscope displays to display all reflected pulses, leaving the problem of interpreting which pulses are relevant and calculating the thickness measurement of the device to the operator.
The present invention improves over the prior art by providing a scheme which is capable of discriminating between various layers of skin and backfat in order to locate the appropriate layer and convert that information to a digital readout in terms of units of length, which can be understood immediately by the operator without further interpretation. Furthermore, the present invention provides a warning indicator to notify the operator that the apparatus has located the appropriate backfat layer so that the operator knows that the data appearing at the readout is accurate. Finally, the present invention performs these tasks without the need for calibration by the operator.